The over-all aim of this research is to analyze the relationships among physiological stimuli (odors), single unit responses, and the neuronal circuitry (synaptic organization) in the salamander olfactory bulb. Since a large measure of the neuronal interactions which take place in the vertebrate nervous system involve neurons in local circuits, we wish to examine the physiological properties of these circuits in the olfactory bulb. In the present proposal we seek to investigate the properties of bulbar local circuits in response to odor by using techniques of precise odor stimulus control, extra- and intracellular recording, horseradish peroxidase staining, and electron microscopy in order to correlate responses obtained using physiologicaly appropriate stimuli with the underlying neuronal circuitry. The salamander has been chosed as a model system for these purposes because of its demonstrated anatomical, physiological, and behavioral advantages. It is anticipated that these studies will provide insight not only into mechanisms by which odors are encoded by the CNS, but also will yield information on elemental aspects of synaptic interactions in the olfactory pathway which may be of general importance for understanding neuronal processing in other central nervous system structures.